The present invention generally relates to sealing joints in moving vehicles, and more particularly relates to an apparatus for sealing a track joint in a track chain of a crawler tractor.
Crawler tractors, such as a bulldozer, typically have a sprocket, an idler, a track chain and a number of track shoes attached to the track chain for propelling the tractor over the ground. During use of the crawler tractor the sprocket rotates and engages the track chain, thereby causing the track chain, along with the attached track shoes, to rotate around a path defined by the sprocket and the idler. The rotation of the track chain causes the track shoes to engage the ground, thereby propelling the crawler tractor over the ground to perform various work functions.
Track chains generally include a pair of parallel chains, with each parallel chain being made up of a series of entrained master links and track links. Track chains further include a series of bushings and pins interposed between and connected to the parallel chains. The bushings and the entrained track links cooperate to form a number of track joints which allow the necessary movement of the bushings relative to the track links during use of the track chain, for example when the track chain rotates about the sprocket and the idler. Track joints are typically equipped with a track seal assembly to keep out various corrosive and abrasive mixtures of water, dirt, sand, rock or other mineral or chemical elements to which the track chain is exposed during its use. The track seal assembly also functions to keep a lubricant within the track joint to facilitate the aforementioned relative movement of the bushings and the track links.
One prior art track seal assembly design used to accomplish the aforementioned functions employs a sealing member axially urged into sliding sealing engagement against a polished bushing face by a resilient rubber load ring. However, a number of problems have been encountered using this seal design over long periods of time.
One such problem relates to grooving of the bushing face. The mixtures of various abrasive particles found in the working environment of a track chain tend to make excellent grinding compounds which can wear grooves into the bushing face. If these grooves become sufficiently deep, the integrity of the track seal assembly can be compromised and abrasive particles can enter the track joint. These grooves also provide a path for lubricants contained within the track joint to leak out. Moreover, since the sealing member slidably contacts the bushing face (i.e. the bushing face is a dynamic sealing surface), a grooved or rough bushing face can accelerate the sealing member's wear as these two elements slide relative to each other. This acceleration can further degrade the integrity of the track seal assembly, thus increasing the probability that abrasive particles will enter the track joint. All of the above discussed problems can result in the premature failure of the track joint and thus the track chain.
Therefore, in light of the above discussion, it is apparent that an assembly for sealing a track joint in a track chain which addresses the aforementioned problems is desirable.
Following one approach, the present invention provides such a track seal assembly that eliminates the use of any of the track joint components (such as a bushing face) as a dynamic sealing surface. In another approach, the present invention provides a track seal assembly which has one or more of its components made of an extremely hard, corrosive and abrasive resistant compound, such as a ceramic material.
Using the above discussed approaches, the track seal assemblies of the present invention provide a durable, reliable, low cost solution to the previously described problems experienced with prior art sealing assemblies. The track seal assemblies of the present invention also isolate its ceramic components from potentially damaging forces generated during the use of the track chain. Moreover, the design of the disclosed track seal assemblies allow them to be retrofit into current track link geometry. Furthermore, track seal assemblies of the present invention eliminate the use of track joint components as dynamic sealing surfaces.